By comparing how gut microbes from human vegetarians and grass-grazing baboons digest different diets, researchers have shown that ancestral human diets, so called "paleo" diets, did not necessarily result in better appetite suppression. The study, published in mBio® the online open-access journal of the American Society for Microbiology, reveals surprising relationships between diet and the release of hormones that suppress eating.
While Western diets have changed dramatically in the last century to become high energy, low fiber, and high fat (think: cheeseburger), our digestive systems, including our gut bacterial colonies, adapted over millennia to process a low-energy, nutrient-poor, and presumably high fiber diet. One idea about the current obesity epidemic is that appetite suppression systems that evolved to work with a paleo diet are off-kilter today.
The appetite-suppressing gut hormones peptide YY (PYY) and glucagon-like-peptide-1 (GLP-1) can be triggered by the presence of short-chain fatty acids (SCFAs) in the colon. Fermentation of plant fiber in the colon by bacteria can produce these SCFAs, so it stands to reason that digestion of a diet high in plant fiber might lead to better appetite suppression.
Gary Frost and his colleagues at Imperial College London in the United Kingdom wanted to test that hypothesis in the laboratory using fecal bacterial samples from three human vegetarian volunteers and from three gelada baboons, the only modern primate to eat mainly grasses.
"Getting to the bottom of how our gut bacteria and diets interact to control appetites is vitally important for tackling the problem of obesity," said Glenn Gibson, co-author on the study based at University of Reading. Frost added, "Understanding how a paleo-like diet impacts the colon's microbiota and the signals those bacteria produce to release hormones that reduce appetite may give us new insight that we can adapt in the modern world."
The team established gut bacteria cultures in flasks and then 'fed' them two different diets—either a predigested potato, high-starch diet or a predigested grass, high-fiber diet. Then they tracked changes in the numbers and types of bacteria and measured the metabolites produced by digestion.
Surprisingly, the human cultures on a potato diet produced the highest levels of SCFAs. Even the baboon cultures fed potato produced more SCFAs than the baboon cultures fed grass. When the researchers applied some of these cultures to mouse colon cells in the lab dish, the cells were stimulated to release PYY hormone. Those exposed to human cultures digesting a potato diet released the most PYY, followed by those exposed to baboon cultures on a potato diet.
This evidence argues that the previous view of paleo diets and appetite suppression is flawed and that high-fiber, plant-based diets likely do not lead to increased SCFAs and increased appetite suppression. Rather, the researchers propose, little to no appetite suppression might help baboons maintain grazing all day to consume enough nutrients.
A closer cataloguing of all the metabolites produced by the bacterial cultures digesting potato or grass diets showed that as the levels of the amino acids isoleucine and valine rose, so too did the amount of PYY released. This relationship was even stronger than that with SCFAs.
"This hints that protein might play a greater role in appetite suppression than the breakdown of starch or fiber," said Timothy Barraclough, another co-author of the study. "More work will be needed to explore the effects of alternative breakdown products of various foods."
The researchers note that this study of digestion in the test tube is limited by not including the roles of gut cells, which absorb and secrete metabolites as well.
mBio® is an open access online journal published by the American Society for Microbiology to make microbiology research broadly accessible. The focus of the journal is on rapid publication of cutting-edge research spanning the entire spectrum of microbiology and related fields. It can be found online at http://mbio.asm.org.
The American Society for Microbiology is the largest single life science society, composed of over 39,000 scientists and health professionals. ASM's mission is to advance the microbiological sciences as a vehicle for understanding life processes and to apply and communicate this knowledge for the improvement of health and environmental and economic well-being worldwide.
Jim Sliwa | Eurek Alert!
About injured hearts that grow back - Heart regeneration mechanism in zebrafish revealed
10.02.2016 | Universität Ulm
Chemical cages: New technique advances synthetic biology
10.02.2016 | Arizona State University
Atomic clock experts from the Physikalisch-Technische Bundesanstalt (PTB) are the first research group in the world to have built an optical single-ion clock which attains an accuracy which had only been predicted theoretically so far. Their optical ytterbium clock achieved a relative systematic measurement uncertainty of 3 E-18. The results have been published in the current issue of the scientific journal "Physical Review Letters".
Atomic clock experts from the Physikalisch-Technische Bundesanstalt (PTB) are the first research group in the world to have built an optical single-ion clock...
The University of Würzburg has two new space projects in the pipeline which are concerned with the observation of planets and autonomous fault correction aboard satellites. The German Federal Ministry of Economic Affairs and Energy funds the projects with around 1.6 million euros.
Detecting tornadoes that sweep across Mars. Discovering meteors that fall to Earth. Investigating strange lightning that flashes from Earth's atmosphere into...
Physicists from Saarland University and the ESPCI in Paris have shown how liquids on solid surfaces can be made to slide over the surface a bit like a bobsleigh on ice. The key is to apply a coating at the boundary between the liquid and the surface that induces the liquid to slip. This results in an increase in the average flow velocity of the liquid and its throughput. This was demonstrated by studying the behaviour of droplets on surfaces with different coatings as they evolved into the equilibrium state. The results could prove useful in optimizing industrial processes, such as the extrusion of plastics.
The study has been published in the respected academic journal PNAS (Proceedings of the National Academy of Sciences of the United States of America).
Exceeding critical temperature limits in the Southern Ocean may cause the collapse of ice sheets and a sharp rise in sea levels
A future warming of the Southern Ocean caused by rising greenhouse gas concentrations in the atmosphere may severely disrupt the stability of the West...
Indications of light-induced lossless electricity transmission in fullerenes contribute to the search for superconducting materials for practical applications.
Superconductors have long been confined to niche applications, due to the fact that the highest temperature at which even the best of these materials becomes...
09.02.2016 | Event News
02.02.2016 | Event News
26.01.2016 | Event News
10.02.2016 | Life Sciences
10.02.2016 | Earth Sciences
10.02.2016 | Physics and Astronomy